A must read research topic on the History of Doitsu Koi and the criteria for judging Doitsu varieties as well as the specific show rules as to which show class a Doitsu Koi should be benched and judged. Written by Willem Daffue.


The aim of this research topic is to find any justification to have separate show classes for Doitsu koi. The criteria for judging Doitsu varieties and the specific show rules as to which show class a Doitsu koi should be benched will also be looked at.

At the recent 45th all Japan Nishikigoi show the Japanese had a separate show class for all Kinginrin koi, but not for Doitsu koi. The SAKKS and the NVN have separate Doitsu show classes but the BKKS not. In Holland, up until 2008 Doitsu B was the most highly contested show class for three consecutive years. The question is whether Doitsu show classes will eventually have the same show status as Kinginrin?

What is the ideal Doitsu koi and how should they be judged? How do you judge Doitsu koi across varieties? This research paper will try and answer the above questions.

History and Physiology of Koi Carp

History of Doitsugoi

To understand and appreciate Doitsu koi as we know them today, it is very important to look back into history and to see where all the specific characteristics of modern Doitsu koi originate.

The first carp were introduced into Japan about 400 to 600 years ago and came from China. These carp belong to the Far East Asia sub specie of Caprinus carpio heamatopterus.

The first German carp were introduced into Japan in the 37th year of Meiji (1904) and belong to the sub specie C.c.carpio. Shinnosuke Matsubara head of the Fisheries Training Department thought that the introduction of German carp would improve the supply of edible fish meat in Japan. Two German scientists, Drs Bruno Hofer and Franz Doffline selected 40 fry of the best quality available in Germany. These fry came out of the ponds of the Earl of Eisch village in the South of Bavaria. 1.


Shinnosuke Matsubara imported the first German carp into Japan. 2.

All 40 fry were transported to Japan during the Japanese-Russo war and sadly only 1 Mirror Carp and 6 Leather Carp survived the trip. These German Carp were immediately introduced into breeding programs and crossed bred with the indigenous carp. This seven Doitsu carp turned out to be the genetic backbone of Doitsu carp and later the Doitsu koi as we know them today.



Archive photograph of the very earliest Doitsu carp in Japan.

In the beginning of the 20th century the Germans already had a very good understanding of genetics. It is very interesting to note what their objectives were when breeding the Doitsu carp, and also where the original genetic material came from.



There is good reason to belief that the original carp came out of the Caspian Sea. From there it found its way to the Aral and Black seas. From there it spread to mainland Asia and also to the west as far as the Danube water systems.

The wild carp is divided in three subspecies: The German carp belongs to the sub specie Caprinus carpio carpio and it originally occurred in the rivers and lakes of Eastern Europe and Western Asia. The other two sub species, Caprinus carpio heamatopterus and Caprinus carpio viridivlaceus occurred in the water systems of East Asia.

In isolated water systems of Europe and Western Asia the sub specie C carpio carpio can even be further divided into eco types. Some of these eco types show definite morphological and even color differences. A very interesting eco type, known today as the striped carp, came out the water systems of Ukrainian. 4

The carp was used as a source of food from very early in history. The first known breeding of carp for food already happened in Roman times. There is good evidence, that between 27BC and 400AD, the Romans actively breed carp for their meat. 5.  As early as 2000years ago people started to move the different carp types between these water systems to breed a carp that is best for food production.




The original German carp (C. c. L) was introduced into the Bavaria area and differed in many ways with carp out of other areas.

Because of the physical characteristics of this carp, it was chosen by the Germans to start breeding programs to produce food. The Germans specifically breed carp for better growth rates and early maturing.

Characterists of Doitsu Carp

In Japan the newly introduced Doitsu carp differed in many ways from their local carp. As in Germany the morphological and physiological characteristics of the Doitsu carp were initially only used to enhance the production of edible fish and not to create ornamental koi. It was only at a later stage that the German carp was actively used to enhance the ornamental koi carp.

The newly introduced German carp did not have scales and was easy to clean and prepared for food. This was actually not the main reason for the introduction of the German carp into the food market as many people still believe today. The main reason was the bulkier body shape and thus more meat to eat. The hybrid vigor caused by the cross breeding of Doitsu and Japanese carp was a major contributing factor in producing more fish meat. The good growth rates and early breeding ages of the German carp was also contributing factors for the importation of the German carp.

The genetic makeup of the German carp is well known and many studies were done in this regard. The German carp show moderate genetic variation with 287 allele and 559 genotypes. 7.

The development of scales in the wild carp and in koi is regulated by at least 2 genes. The gene S is designated to indicate the formation of scales and its mutant or allele s indicates no scales. Another gene called N stops the formation of scales and its allele n does not interfere with the formation of scales at all. 8

The following table shows the specific genes that determine the different scalation types: 9

1.  Scaled carp - SSnn and Ssnn.

2.  Mirror carp - ssnn.

3.  Striped carp - SSNn and SsNn.

4.  Leather carp - ssNn.

Scientist did find specific loci on the DNA molecules of carp that regulate body shape. Four genes or loci were identified that is associated with body shape. The locus HLY319 and HJL693 determines body length. Of these two genes HLY319 seems to be the more important one. The loci HLY693 determine the weight of the fully grown carp. Another gene HLY677 determines the width of the carp. As a combination the above mentioned genes determine the overall body shape of the carp and of koi as well. 10

Physiological differences between Japanese carp and Doitsu carp:  11

Doitsu carp grow remarkably well and outperformed the local carp with better growth rates.

Because of these superior growth rates Doitsu carp are hearty eaters.

They mature early and females especially spawn at an early age.

When Doitsu carp where used in breeding with other carp the offspring show very strong hybrid vigor.

They age at a faster rate and do not reach the same old age as Japanese carp.

Doitsu carp show less resistance towards diseases.

Morphological differences between Japanese carp and Doitsu carp: 12

The body shape of the Doitsu carp was more rounded and shorter when compared to the Japanese carp.

The scalation on the Doitsu carp differs from the scalation of Japanese carp. There are four basic scalations to be found on Doitsu carp:

Scales only on the back, almost symmetrical on both sides of the backbone.  Mirror carp.

Two rows of scales from the head to the tail on the back as well as two single rows of scales along the lateral lines.  Striped carp.

Fish with no scales at all. Leather carp.

Fish which have random exaggerated scales strewn about their bodies.


This mirror carp demonstrate the typical Doitsu body conformation.



These striped carp show characteristic scales along the lateral line.

The differences between Japanese and German carp.



It is important to have a good understanding of these differences because today most koi inherited characteristics of both the Japanese and the German carp.

Breeding Doitsugoi and Nishikigoi

Doitsugoi was first bred with Nishikigoi about 100 years ago. The pioneer who introduced Doitsugoi to Asagi was Kichigoro Akiyama and in the 41th year of the Meiji era (1908) he produced a new variety we know today as the Shusui. 13

The most obvious difference was the scalation on the newly produced koi. Less obvious but as important were the body shape changes that took place. The long and much thinner body conformation of the Japanese koi changed to the beautiful bodies of modern koi. Almost all koi varieties today do have Doitsugoi blood in their genetic makeup. The superb body shapes off modern show winners would not be possible without the genetics inherited from the Doitsu carp.

The inheritance of scalation is more predictable than color because less genes control scalation. As we have seen under the heading characteristics of Doitsu carp, the inheritance of scalation is controlled by two genes, associated with their mutants. All scaled koi caries the gene S that is responsible for scale formation. The S Gene has an allele s that lacks the ability to produce scales.  Another gene called N and its allele n also adds another factor to scale formation. The gene N stops scale formation but the allele n is not able to stop scale formation. 14

Crossing koi with all these above mentioned genes controlling different aspects of scalation produced many different possibilities of genetic combinations. The outcome was koi with many different scalation types.

As was the case with the original German carp the newly bred koi produced five basic scalation types. 15

Fully scaled koi: (Wagoi or also called normal koi.)



Koi with no scales at all: (Leather koi.)



Koi with scales only found on the back: (Mirror or Kawigoi)



Koi with scales on the back as well as the lateral line: (Striped or Kagami goi)



Koi which have random exaggerated scales strewn about their bodies: (Armored or Yoroigoi.)



Skin Structure in Doitsu Koi

Scales have many functions and are therefore actually very complex in structure. One of the most important functions of scales is to keep the skin rigid and stiff. In Wagoi the scales keep the skin smooth and uniform. Without scales the skin of Doitsu koi tends to pit and wrinkle much easier and is a major factor in the early aging of the skin. Small skin and subcutaneous lesions show up as irregularities on the skin itself. Wrinkles can also distract from the beauty of the skin.



This photo was taken on the Durban show and clearly demonstrates the effect of wrinkles and irregularities on the quality of the skin.

Scales create multiple layers of color, depth and refinement. The structural changes in the skin caused by the introduction of Doitsu blood also changed the expression of color in a major way. Scales are one of the most important structures in the skin and without it the way we will see color on koi changed.


Histology of a koi skin to show that the erythrophores originate in the upper dermis and can also be found in the epidermis. 16


Histology of a koi skin to show that melanin originates in the deep dermis layers. 17

Color pigments originate in different layers of the skin and the position above or below the scales influence the expression of that color. The lack of scales creates the effect off a single layer of color. Fukurin created by scales also add to the effect of depth and refinement and is absent in Doitsu koi.

Sashi, the effect created by scales underlying chromatophores (pigments), is also lost in Doitsu koi.


The outermost layer of the dermis contains the erythrophores (red pigment). Because scales develop in the dermis below this red layer, the influence on the color expression is minimal. Only in young koi or koi with underdeveloped shiro do the scales have an impact on color expression. The bases of scales covered with hi underlying scales covered with weak shiro create the pinkish edge called sashi. Sumi can create a similar effect. In Doitsu koi this effect of sashi is lost because of the lack of scales.

Melanophores responsible for the sumi in koi are found in deeper layers of the skin. The Melanopblasts produce melanin or black pigment that can be distributed throughout the dermis but most often originate in the deep dermis below the scales. In scaled koi the black needs to develop, or almost grow through or around the scales to reach the surface, creating a three dimensional effect. Doitsu koi do not have scales and sumi expresses itself almost as a flat layer of black on the skin. The combination of pigments, reflective guanine, dermal fibers and skin structures create the color of our koi. Without scales the skin structure changed dramatically and this also has an effect on our appreciation of skin quality and luster.

Is There Any Justification to Seperate Doitsu from Wagoi Classes at Koi Shows?

In Japan kinginrin koi do have separate Kinginrin show classes for almost all varieties. Because of the differences in skin structure, the Kinginrin kio's appearance differs enough from Wagoi to justify separate show classes. The skin structure of Doitsu koi differs even more from Wagoi but does not have separate show classes. It is however clear that difference in appearance between Wagoi and Doitsu koi, and the scientific anatomical studies of different skin structures, not going to answer any of the above questions.

It is therefore important to test the opinions and "feelings" of knowledgeable koi enthusiasts to decide whether Doitsu koi should have separate show classes or not. A well conducted survey is properly the only way to address the above problem.

A survey was done to test the opinions of people that are involved in koi shows. The idea was to get the opinions of qualified judges of the different chapters in S.A. as well as most koi keeping countries in the world.

Results of a Survey done in 2010

  • 55% of respondents felt that Doitsu koi deserve separate show classes.
  • 80% of above mentioned respondents (said yes to separate Doitsu classes) felt that a Doitsu A and B class would do.
  • 20% respondents wanted separate classes for all Doitsu koi.
  • All European (excluding Britain) and U.S.A. respondents justified separate Doitsu classes, provided that the number of entries is high enough.
  • 40% felt no need for separate Doitsu classes.
  • 80% of respondents in 1 thought that the numbers of show entries will eventually determine if Doitsu koi would show in separate classes.
  • 22% said separate Doitsu show classes were not practical because of the time it would take to judge the extra classes.
  • 11% felt that separate Doitsu show classes would duplicate judging as they would have to compete against each other for the bigger prizes anyway.
  • 22% anticipated complications when judging across varieties.

One respondent suggested a single Doitsu class for Doitsu gosanke and Doitsu utsuri. The other Doitsu varieties could compete in the normal show classes.

A single conversation with a Japanese judge at the 2010 SAKKS nat. show confirms the status of the current situation in Japan (No separate Doitsu classes for most shows). The latest development in Japan is very interesting because the largest show, the AJNPA all Japan show, now has a specially set Doitsugoi division.

The results of this survey indicate a big difference of opinions among koi enthusiasts. There are also clear differences of opinion in the different regions and countries.

A few conclusions can, however, be made:

Most people feel that in the future Doitsu koi will show in separate classes. The process will be gradual and it will depend on the numbers of entries. There will be more prizes to win and that will encourage more entries. The opinion of the Japanese is probably going to dictate the tempo for change and the status of Doitsu show classes in future.

There is a definite development or movement towards separate Doitsu show classes across the spectrum of koi societies in al koi keeping countries. Together with the morphological differences, the following recommendation can be made.

Some Thoughts and Suggestions

Doitsu koi should show in separate Doitsu A and Doitsu B classes. Doitsu A will be gosanke and Shiro utsuri and Doitsu B will be all the other varieties. The separate show classes for the Doitsu koi pertain to all sizes. If the number of entries at a particular show does not allow for separate classes for all sizes, sizes 1 to 5 and sizes 6 to 9 can be grouped together. If there is still not enough entries at a particular show all sizes have to compete in a single Doitsu A or Doitsu B class for all sizes.


At the 45th ZNA all Japan koi show the Kamiya prize for Kawarimono was won by this Doitsu koi.  18

In What Show Classes should Doitsu Varieties be Benched?

Example Shusui and Kumonryo?

Since 1908 when the first Doitsu variety the Shusui was created, many other varieties developed because of cross breeding with Doitsu blood lines. Many of these varieties are not recognized yet but others are well established.

The problem arises when established Doitsu varieties qualify for more than one show class. Should Shusui be benched in the Doitsu class or under Shusui? Can show organizers allow the owner to decide if a specific Doitsu koi should be benched in its main show class or in a Doitsu class or will clear and specific show rules be the answer to this problem.

To illustrate this problem we can look at the Doitsu Kohaku in the photos below.


If the Doitsu Kohaku on the left compete in the variety class, it has to compete against the Wagoi Kohaku on the right.



In a Doitsu A show class the same Kohaku now show against all Doitsu Gosanke.

Doitsu variants of Gosanke and Shiro Utsuri have difficulty competing with their scaled counterparts. Doitsu variants of other varieties can compete very well in their specific classification.


Both Doitsu koi in the above photos can compete against a very good Ochiba in the Kawarimono group.

It is just impractical to have a show class for every variety and therefore the question is whether clear rules should dictate in which class a specific koi will be benched. It is very important that whatever rules apply, that they will be fear, give the specific koi the best opportunity to do well, and promote the variety.

Interesting new varieties originate by cross breeding Doitsu koi with Matsuba, Ogon and Ginrin koi.  Some of the new varieties can be benched in more than one show class.


21hodk 22hodk
Doitsu / Ogon (Doitsu Kujaku) Doitsu / Ogon / Koromo (Shockikubai)

Both these koi can be benched as Doitsu B or Hikari Moyomono or Kawarimono.

Both the Shockikubai and the Doitsu Kujaku can technically be benched in more than one show class. The Shockikubai and Doitsu Kujaku are Doitsu koi and can therefore show in the Doitsu B class. Both koi are also Ogon koi and can be benched in Hikari moyomono. In Japan the Doitsu Kujaku and the Shockikubai can also be benched in Kawarimono. This example is to illustrate why it is important to have definite and clear show rules for benching koi.



Shusui with Ginrin scales.                      A young pearl Shusui possessing Ginrin scales.

Both koi in the above pictures adds another interesting factor to the problem. These Shusui are also Ginrin koi and can therefore be classified in the Ginrin B class. It is very interesting to note that some literature will classify both koi as Ginrin although there is only one line of Ginrin scales on a side.  Some authors give the definition of a Ginrin koi as at least three rows of Ginrin scales on a side of a particular koi before it can be regarded as a Ginrin koi. This definition of Ginrin means that a Doitsu koi can technically never be classified as a Ginrin. This is ironic because Ginrin originally derived from Doitsu bloodlines. 19

If a particular koi can be classified as a Ginrin or a Doitsu koi, another problematic situation is created as can be seen in the example below. In this particular scenario one has to decide which variety class is carrying more weight, the Ginrin or Doitsu class. A specific rule should clearly guide the benching team in this situation.


Ginrin Doitsu Ochiba                         Doitsu Ochiba in a Doitsu B class.




Ginrin Doitsu Ochiba    versus            Ginrin Ochiba in a Ginrin B Class.

In many shows in Japan, do Doitsu koi compete in the Kawarimono group. The metallic Doitsu varieties that originate from the Kumonryu lines are traditionally benched under the Kawarimono group. Even Doitsu Kujaku is sometimes benched under Kawarimono. See example on page 17.

Again a survey was done to determine the opinions of well-informed koi enthusiasts over the world.

  • 66% felt that Shusui should show in the Asagi/Shusui class.
  • 34% thought that all Doitsu varieties should show in either Doitsu A or Doitsu B.
  • 20% felt that Doitsu koi should show in their own variety classes.
  • 22% of respondents thought that Kumonryu belongs to the Kawarimono variety.
  • 78% of respondents would bench Kumonryu under Doitsu B.
  • 11% thought that the owner should decide in which variety his koi should show.

It is clear out of this survey that there are big differences among koi enthusiasts on what the appropriate show class for a specific Doitsu koi will be. There is however a few conclusions that can be made out of this survey.

Shusui is a well-established variety and historical as well as genetically it belongs to the Asagi group. It is thus no surprise that the majority of respondents do not want to change the current situation where Shusui show in the Asagi/Shusui class. The Ginrin Shusui or Pearl Shusui will also be benched as Asagi/ Shusui and not as a Ginrin B.

Also significant was that the majority of respondents feel that all other Doitsu koi should show under either Doitsu A or Doitsu B. Even Kumonryu that is a well established variety and is traditionally benched under Kawarimono will then be benched as Doitsu B. With a separate Doitsu show class most respondents will bench Kumonryo under Doitsu B. Another example is the metallic Doitsu varieties that are traditionally benched under the Kawarimono group or Hikari moyomono will now be benched under Doitsu B.

All Doitsu koi that qualify for the Doitsu B variety class can usually compete very well in their specific variety classes. Even at Japanese shows nowadays, Doitsu koi do take first prizes in their specific variety classes. One respondent suggest that only a Doitsu A class for Gosanke and Shiro Utsuri will do because he feels that all other Doitsu koi will be able to compete well enough in their specific variety classes.

At the Durban show a very interesting show rule applied where the owner could decide in which variety class he wants to show his koi. If the owner could not decide, the benching team had to make the decision in which variety class the particular koi should show. This ruling brought a very exiting dimension to the benching procedures. The flexibility of this rule was well received by some of the benching teams.

Most owners know exactly in which category they want to show there koi. Most of the owners was well informed and had a good idea where their koi will do best on the show. In the cases where the owners was not sure or do not know at all, it was very exciting for the benching teams to make that decision.

Only 11% of respondents support this rule but personally I feel that this rule can be given serious consideration. The conditions for this rule is that the benching team should be happy that the owners decision is technically correct, or in the case where the benching team have to make the decision, that the koi should show in the class where it will do best. It is also very important to discuss the decision with the owner and make sure that he or she understands the reasons for benching the koi in a specific show class.

Before a recommendation can be made, we must decide what the objectives for benching Doitsu koi will be;

  • The decision should be fear.
  • Give the specific koi the best opportunity to do well.
  • Promote the variety.


According to the Survey the following proposals can be made:

Shusui is a well-established show variety and its status as a separate show class should be kept as it is. All Shusui, as well as the Ginrin or Pearl Shusui, will be benched under the Asagi/Shusui variety.

All other Doitsu koi should then be benched under either the Doitsu A or Doitsu B categories. Doitsu A will be Gosanke and Utsuri and Doitsu B will be all the other varieties.

If we accept that Doitsu koi can be classified as Ginrin the following rule should apply. If any koi can be classify as either a Ginrin or a Doitsu variety it should be benched under Ginrin. In the case of the Pearl Shusui it should be benched under the Asagi/Shusui variety.

All Doitsu Ogons (metallics) with two or more colors should be benched under Hikari Moyomono. All single colored metallic (Ogon) Doitsu koi will be benched under Hikari Mujimono. Show rules should clearly specify as to which show class a specific koi should be benched.  The above recommendations are simple and straight forward,


Personally I disagree with the above recommendation. The flexibility, fun and the challenge of benching interesting koi in the show classes where it will do best appeals to many koi enthusiasts. The extra Doitsu show classes create more opportunities for more koi to participate and do well on shows.

If we look at the objectives set out previously namely; that the decision will be fear, give the specific koi the best opportunity to do well, and promote the variety, we have to admit that the previous recommendation not adhere to these objectives. Interaction with owners is also lost with above rigid rules.

My proposals would be as follows:

The ruling on Shusui stays as in the above recommendation. For the rest of all the Doitsu entries the owner or benching team can bench the koi in any show class where it fit and it will do best.

What Should the Judging Criteria be for Doitsu Varieties?

As we discussed under the heading, characteristics of Doitsu koi, there are a few basic differences between Doitsu koi and Wagoi. The four main differences are body shape, skin structure and quality, scalation and the expression of color. To discuss any criteria for judging Doitsu koi we need to keep these four basic differences in mind. We will discuss each one of these basic differences in detail.

Body Shape

The cross breeding of Doitsu and Wagoi koi lead to the beautiful fuller body shapes of modern koi. It is an undeniable fact that Doitsugoi blood has deeply penetrated Nishikigoi. Many Japanese breeders feel Doitsugoi most important contribution towards modern koi is body shape. 20

Many Doitsu koi however tends to have to short and to deep body shapes. This type of body shape is less appreciated and also causes the koi to move less graceful through the water.

To evaluate the Doitsu koi for body shape the same criteria apply as for Wagoi koi. Most of the respondents in the survey agree that body shape a very important aspect is, when evaluating Doitsu koi. Short and fat body shapes tends to be genetically dominant. 21 When evaluating Doitsu koi we must be aware of the tendency for shorter and fatter bodies.


Above photos illustrate the difference in body shapes between Wagoi and Doitsu koi.



This Doitsu koi have the ideal body shape. The body is symmetrical, imposing, strong and well balanced.

Skin Structure and Skin Quality

Because of the lack of scales, the skin's structure changed in such a way that it can influence its appearance. Uneven skin and especially wrinkles can distract from the beauty of the skin. In Doitsu koi the skin tends to lose its quality much faster than Wagoi. The typical leather effect sets in at an early stage and Doitsu goi's show life is much shorter then Wagoi


The typical leather effect on a Doitsu koi.


Wrinkles and irregularities on a Doitsu koi.

Skin quality is of major importance in the appreciation of Doitsu koi. The quality of the show koi is in a big way determined by body shape and skin quality. The skin should have a lot of luster, must be shiny and there should be no irregularities.

Because so many factors determine skin quality, there are maybe hundreds of genes involved. Scales keep the skin rigid and this is a major factor in determining skin quality.


This koi presents good skin quality with luster and a waxy porcelain texture.


Scalation is almost certainly the most obvious difference between Doitsu koi and Wagoi. The judging criteria on the scalation of Doitsu koi is also the most controversial aspect among the respondents in the survey. There are different opinions on which type of scalation is preferred.

We will discuss each scalation type in detail to get to the best possible recommendation.


Kagami goi

Kagami goi is also known as mirror koi, ladder koi and striped koi. The Kagami goi is a Doitsu koi with scales along the entire top of the body and along the lateral lines. It is important to note that the scales, on the top line of the Kagami goi, stretched from immediately behind the head right up to the tail.


Kagami goi with scales on the top line and the lateral line.

Kagami goi rarely achieve good symmetry and continuity of scalation. If they do this type of scalation can be very attractive. Both the dorsal scales and the lateral scales should be uniform in size, uninterrupted and perfectly aligned. 12% of respondents in the survey preferred this scalation.

Sometimes Kagami koi do not have scales on the lateral lines and can be confused with Kawi koi. In Kagami koi the scales are big and most of the time stretch from just behind the head up to the tail.

This is the type of scalation that is preferred on the Shusui. Again the scales should be of uniformed size and start right behind the head and run up to the tail. Uniformity, symmetry and continuity of the scales along the entire length of the dorsal line are of utmost importance. Most of the respondents in the survey preferred this scalation type.

Just behind the head, some Kagami goi tends to have large irregular scales. These scales are not appreciated. In appreciation of koi the area behind the head is very important. Bad scalation on the shoulder is a serious demerit in Doitsu koi because this area is a major focal point when judging koi.


An example of bad scalation behind the head.


Compared to the previous photo we can say this is better but still not good.


Although this koi do have irregular clumps of scales behind the head it is acceptable because it is small and balanced.

Floating or random scattered scales on Kagami goi is also a problem. These muda goke (wasteful scales) distracts a lot from the beauty of Doitu koi. These floating scales can be found in all scalation types but tends to favor the Kagami scale type. In Doitsu varieties muda goke are a serious defect, however if the muda goke cannot be seen from above it is considered less of a defect.


Muda goke or wasteful scales.



The koi on the left did very well at the 45th ZNA all Japan in spite of the Muda goke as indicated by the arrows. The reason for this is that the scales are on the side of the body and not that clearly visible. The koi on the right have colorless Muda goke and is not that obvious.




An example of good scalation in a Doitsu koi.



A break in the continuity of the scalation.


This Shusui expresses the almost perfect scalation type. The random scales just behind the head distracts a little bit from the beauty of this koi. This important area out of a judging point of view tends to be ruined by irregular scales.

Kawi goi

Kawi goi are Doitsu koi with scales only along each side of the dorsal fin. Kawi goi is also known as leather koi. In some literature the Kawi goi is also known as mirror koi but this name is more applicable on the Kagami goi. The scales in this type of Doitsu koi tends to be much smaller.

Kawi goi can be exceptionally attractive and 22% of respondents favor this type of scalation. In this type of scalation there is less scales and the scales tend to be smaller as well. Judging the Kawi goi therefore demands an even higher standard. Scalation should be uniform in size, symmetrical, well aligned and uninterrupted. Sometimes the scales on the Kawi goi can have a metallic luster that adds an extra factor of beauty. This metallic luster is caused by

(36) crystallized guanine that is deposited on the scales. Most of Doitsu Gosanke tends to be of the Kawi goi scalation type.




Two Kawi goi illustrating the typical scalation along the dorsal fin.

Yoroi goi

Yoroi goi is Doitsu koi where most of the body is randomly covered with irregular size scales. These scales tend to be larger than normal scales. The Yoroi goi is also known as the armored koi. Most of the time this scalation type lacks uniformity and tends to be messy. In rare instances where a Yoroi goi achieve symmetry, a very interesting and attractive koi can be produced. In spite of these rarities the Yoroi goi scalation type is not favored.


Above is a good example of a Yoroi goi.


43hodk 44hodk
Different scalation types of Yoroi goi. Both these photos were taken at a koi show illustrating the point that at least same koi enthusiasts like this scalation type.

Most respondents in the survey dislike the Yoroi goi type of scalation. The responses vary from not acceptable to hideous.

Interesting was the fact that a lot of Yoroi goi turned up at shows in S.A.  Many koi enthusiasts enjoy keeping and show there Yoroi goi.

It will be interesting to see what the Yoroi goi will produce in future. The fact that some Japanese breeders try to perfect this scalation type implicate that the status of the Yoroi goi will change in future. For a Yoroi goi to reach the front page of an important koi magazine in Japan tells us something about the changing status of Yoroi goi.


Above is a picture of a Yoroi goi on the front page of the Nichirin koi magazine in Japan. The owner bought this koi because he liked the scales witch reminded him of the armor of a Samurai warrior.

Scalation that does not fit in any of these three scalation types

All Doitsu koi today originate out of only six Kawi goi and one Kagami goi. From the onset these koi were cross bred with each other and with other Wagoi. Most of these Doitsu koi can be classified in anyone of the above scalation types, but many in between scalation types are also common. Most of these in between scalation types are messy and give the impression of incompleteness. Out of a judging point of view these forms are not appreciated.


This Doitsu koi (above) does not fit any of the scalation types and can be described as a scalation type that has characteristics of both Kagami goi and Yoroi goi.

The perfect scalation type will be the Kagami type without any scales on the lateral lines. The scales must be of uniform size and stretch from the head to the tail. The scales must be neatly aligned and uninterrupted. The absence of any floating scales, especially behind the head and dorsal body areas is important. Because the scalation on Kawi goi is simpler, the criteria have to be very strict.  Especially in Gosanke, Kawigoi can be the scalation of choice.



Two Ogon koi with equal quality but the type of scalation differs.

Personal opinion is going to play a role in this instance.


In Doitsu koi we have to look at color on the scales itself and then also at the expression of color on the areas without scales. It is important to distinguish between these two colors effects on Doitsu koi.

Colour on the scales itself

It is possible for Doitsu koi to be divided into two groups by the colored or non colored scales. Colored scales add a new dimension to a koi. In varieties like Shusui and Doitsu Kujaku the colored scales give impact and status to the koi. Because colored scales are mostly black or indigo they contrast very well with the other colors on the koi. Contrasting colors created by the dark scales is eye catching and appeals to many koi enthusiasts.

Scales are colorless but certain deposits on the scales create color effect. These deposits are not color pigments, but minerals that create the effect of color. These scales are mostly black in color but a special effect is created by fibers in the dermis and the black color change to a deep blue. These blue or indigo colored scales can be seen in certain varieties like Shusui.

Colorless scales create a very different effect. This effect can be described by words like elegant, beautiful and graceful. This softer but more elegant effect lacks the impact of the dark colored scales.


The deep indigo blue of colored scales next to colorless scales on the same koi.


The difference in appreciation of these two koi  are dramatically influence by the coloration of the scales.


Both these photos illustrate the effect of colored scales.

Colour on the Scaleless Skin

Scales do have an effect on how color expresses itself on the koi skin. Scales and Fukurin create the effect of multiple layers of color and the lack of scales means a single layer of color. To breed Doitsu koi with thick solid color is more difficult than in Wagoi.

In Doitsu koi the absence of scales means that there are no structures that interfere with kiwa between colors on the skin. Sashi the color effect created by scales cannot be found in Doitsu koi. The quality of the color and specifically the kiwa in Doitsu koi should be extremely sharp as there are no scales to blur the effect.

Al participants in the survey stressed the importance of consistent and uniform color with good kiwa.


This koi illustrate good luster, uniform color but the kiwa could be better.


The color on the head and the color on the body are exactly the same. The kiwa on the anterior aspect of the hi plate on the body is very good.

When judging color on Doitsu koi it is important to look for thick consistent uniform color that show luster and good sheen. Kiwa should be crisp and sharp. Doitsu koi should have exactly the same hue of color on the head as it has on the body.

What is the Basis for Judging one Doitsu variant against another Different DoitsuVariant in the same show Class

When judging Doitsu koi across varieties the basic criteria will depend on two principals. Firstly the basic principles of Doitsu characteristics should be looked at. Secondly, the appreciation rules for the specific variety should then also be looked at.

Judge the Doitsu Characteristics of a Koi

All the criteria that we discussed under point 2.4 apply when judging any Doitsu koi. As always we should start with body shape and be aware of the tendency for fat and to short bodies. Secondly we must look for good skin quality. The skin should be smooth, without wrinkles or pitting, and show good shine and luster. Scalation is the next characteristic to look at. If Kagami scalation achieves good symmetry and continuity it is the preferred scalation type. Kawi scalation is also highly rated. Color is the last of the basic Doitsu characteristics to look at. Dark colored scales can create dramatic contras and impact. Colorless scales create the effect of refinement and elegance. Color on the body should be thick uniform and with good kiwa.

Judge the Appreciation Points of the Specific Variety

The specific variety criteria are the second set of judging criteria that should be applied in judging a Doitsu koi. It is very important that a Doitsu koi should also meet the judging criteria of the specific variety. A Doitsu Kohaku for example should display a snow white background, solid and homogenous hi, and a well balanced pattern.

The judge should integrate all the above criteria to reach a conclusion as to which koi is the best on the day. The wow factor or impact of a certain koi can be judged against the elegance and refinement of another koi. Because of the complexity of the Doitsu scale types, judging criteria became very interesting and can be stimulating to judge. To judge Doitsu koi across variety classes should be a challenge and not a problem.


The dark scales of the Kikokuryu on the left, accentuate the Doitsu characteristics of this koi in such a positive way that most judges will probably rate this koi better as the Kin Kikokuryu on the right.


The koi on the left presents very good Doitsu characteristic with the highly rated Kagami scalation while the Showa on the right shows bad scalation of the Kawi type. The scales on either side of the dorsal fin are uneven and the two sides do not even look the same. The rest of the koi is spectacular. What weighs more out of a judging point of view, the scalation or all the other characteristics of body shape, variety ext?


The koi on the left presents good show qualities but have bad scalation which is accentuated by the dark scales. The koi on the right present's good Kawi scalation but with a bad body shape and lack of luster.




The above photos appeared in Japanese koi magazine on how to judge Kawarimono. Note that the Doitsu varieties were benched under the Kawarimono group, and that the judging across varieties not be considered as a problem.


Summary of Judging Criteria for Doitsu Koi

When a Doitsu koi is presented for judging, the first task of the judge is to determine if the koi was benched in the correct show class. If a Doitsu koi is benched in the correct show class it implicate that the koi meets the criteria for that show class or variety and that the koi will be able to compete to the best of its potential in that specific show class.

The Doitsu koi can then be judged according to the following three principals.

  • All the basic rules that also apply for other varieties:
  • Body shape
  • Skin quality

Criteria that apply for specific Doitsu characteristics.

  • Type of scalation
  • Color of scales
  • Neat, uniform and even scalation
  • No floating scale

Criteria for judging the specific variety

  • Color
  • Kiwa
  • Pattern
  • Variety criteria



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M. Flajshans and G. Hulata  "The common carp"

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Satoru Hoshino and Shuji Fujita  "Nishikigoi Mondo"  p48

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Dr. H. Axelrod  "Koi Varieties" p54

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Satoru Hoshino and Shuji Fujita  "Nishikigoi Mondo"  p48

Satoru Hoshino and Shuji Fujita  "Nishikigoi Mondo"  p48